The present invention relates to a method and apparatus for measuring a concentration of a species in a portion of an atmosphere of a furnace, in particular a concentration of an alkali metal species (such as sodium) in a portion of the atmosphere of a glass making furnace.
It is known that alkali vapour, in particular sodium, plays an important role in the corrosion behaviour of refractory materials used in glass making furnaces.
Methods are known using extractive sampling to determine the level of sodium in the atmosphere, but such methods are time consuming and do not provide continuous monitoring.
Methods are also known using laser induced breakdown spectroscopy. Such systems are expensive and require high power lasers.
It is also known to use the absorption of visible light traversing the furnace atmosphere to measure the absorption due to sodium atoms. Such a system requires two holes in the furnace (one in each opposing sidewall) and as such increases the likelihood of cold air ingress into the furnace. Also it can be difficult to accurately align the light source with the detector.
There is therefore a need for a method for determining the concentration of sodium that may be in a furnace atmosphere that at least partially overcomes the above problems.